A screen reader needs to know what a piece of a page is, not only what it looks like. The ARIA role complementary describes supporting content related to the main page but not essential to it.
What this role means
Supporting content related to the main page but not essential to it.
ARIA roles add meaning to the accessibility tree. They do not automatically make something clickable, move keyboard focus or build an interface. Those behaviors come from native HTML controls or from correctly implemented JavaScript.
See complementary in a real page
<aside aria-label="Related lessons">
<h2>Practice more</h2>
<p>Review headings and lists.</p>
</aside>Read the example
You may notice that the snippet does not write role="complementary" explicitly. That is intentional: the native element already communicates this meaning, so repeating the role would add unnecessary markup.
The aside element normally supplies complementary semantics.
When to use it
Start with native HTML whenever possible. Add ARIA only when it provides missing meaning for an interface that you cannot build with the appropriate native element.
In an accessibility inspector, compare the accessible role and name with the visible content. The important goal is that both keyboard users and screen-reader users can understand the page.
Try it yourself
Put the example on a practice page and inspect it using your browser accessibility panel. If it includes interactive controls, reach them with Tab and check whether they work without a mouse. Explain whether the semantics come from native HTML or an explicit ARIA role.
Common Beginner Mistakes
- Adding
role="complementary"without checking whether an ordinary HTML element already supplies the right semantics. - The aside element normally supplies complementary semantics.
- Confusing the role announced by a screen reader with the behavior that the browser implements.
Key Takeaways
complementaryis related to supporting content related to the main page but not essential to it.- The aside element normally supplies complementary semantics.
- Native HTML is the first choice; ARIA should clarify meaning, not replace working HTML.